The present invention relates to an image taking lens unit with an image pick-up element chip incorporated in a lens mount frame.
Conventionally, an image taking lens unit has a lens mount frame normally including a plurality of lenses, a flat plate-like optical element, such as an infrared (IR) cut filter, and a substrate with an image pick-up element chip mounted thereon. The optical element and image pick-up element chip mounting substrate are held in a recess in the lens mount frame with a cushion rubber provided between the optical element and the chip. A resultant structure is covered with a mounting member, which is then fixed by screws, etc., to the lens mount frame, so that the optical element and image pick-up element chip mounting substrate are mounted in place on the lens mount frame.
In an electronic image taking device using such an image taking lens unit, a current tendency has been speedily toward obtaining a compact and low-cost unit. Therefore, there is a growing demand for a compact and low-cost image taking lens unit itself.
The present invention has been achieved with such a current situation in view and the object of the present invention is to provide a compact and low-cost image taking lens unit.
The image taking lens unit according to the present invention comprises an image taking optical system for forming an image of an object, an image pick-up element mounting substrate having an image pick-up element chip for receiving the image, and a frame member for retaining the image taking optical system and image pick-up element mounting substrate in place. The image pick-up optical system includes a lens, which has an entrance optical surface near the object and an exit optical surface near the image pick-up element chip, both of which are opposite to each other. The frame member has lens positioning face for positioning the lens and substrate positioning face for positioning the image pick-up element mounting substrate. The lens positioning face and substrate positioning face cooperate to align a center of the lens and a center of the image pick-up element chip and position the lens and the image pick-up element chip with a suitable distance.
The image taking lens unit allows the image taking lens and image pick-up element mounting substrate to be easily set in the frame unit. At the setting time, lens positioning face and substrate positioning face cooperate to align a center of the lens and a center of image pick-up element chip, such that centering adjustment is made automatically. Further, the lens positioning face and substrate positioning face cooperate to position the lens and chip with a suitable distance based on the lens design data, which allows the chip to be on an image formation plane of an image pick-up optical system. Therefore, the generation of a focusing blur resulting from a displacement from an optimal distance between the lens and the chip is automatically prevented. As a result, the assembling accuracy and productivity are both improved.
The substrate positioning face is preferably formed on an inner wall surface of the frame member so as to facilitate the assembling of the image taking lens unit on an associated device.
The lens positioning face may be either on the outer peripheral surface of the frame member or on the inner wall surface of the frame member. However, in order to achieve a compact image taking lens unit and readier assembly of the image taking lens unit on the associated device, the lens positioning face is preferably on the inner wall surface of the frame member.
The lens may comprise not only a single lens but also a cemented doublet lens. Further, the image pick-up optical system may have any other lens and, in accordance with the addition of such a lens, the frame member may have corresponding lens positioning face. That is, the image pick-up optical system may have a plurality of lenses and the frame member may have a corresponding member of lens positioning faces.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.